Selective degradation of nylon 6,6. I. Description of the degradation technique and preliminary morphological characterization

Abstract

A technique for the selective degradation of amorphous regions in nylon 6,6 is reported. Samples of unoriented film and single‐crystal mats have been subjected to selective degradation by refluxing in hydrazine. Weight loss, viscosity‐average molecular weight, density, and small‐angle x‐ray scattering of these samples were monitored as a function of time of degradation. In addition, selected samples have been investigated by gel permeation chromatography (GPC) and transmission electron microscopy. Based on the results of these investigations it is concluded that the reported degradation technique is unique in that the debris is not monodisperse in molecular weight distribution. The Weight loss, density, small‐angle x‐ray scattering, and microscopy data demonstrate that the unordered or noncrystalline regions of the material are removed upon treatement. However, the relatively high molecular weight and broad molecular weight distribution of the debris indicate that regular folds at lamellar surfaces are intact after degradation treatment.

Selective chemical etching of poly(ethylene terephthalate) using primary amines

“…The intrinsic viscosity is related to the molecular weight and should develop a limiting value with degradation time if only crystalline structures remain. 4 The results of these measurements are shown in Figure 4. The sample at 12 hr is almost completely degraded (see Fig.…”

Selective degradation of nylon 6,6. II. Application of the degradation technique to commercially drawn fibers

“…4 of ref. 8) to estimate the peak broadening associated with the GPC instrument at these conditions. At molecular weights lower than that corresponding to the maximum, distinct, reproducible "humps" can be seen on the chromatograms; these aided the curve resolution.…”

“…Shrinkage under the conditions used for selective degradation was less than 6%, and there was no evidence for additional crystallization. 8 The objective of the present research was to use our recently developed techniques for selective removal of amorphous regions in nylon 6,6 to characterize commercially drawn yarn. After removal of the amorphous regions by the degradation process, the remaining crystalline material was available for direct examination.…”